JP5224630B2 - Method for accelerating curing of adhesive - Google Patents

Description

(Technical field)
The present invention relates to a method of heating an adhesive composition filled with particles using an alternating magnetic field . The invention also relates to a method for bonding metallic and non-metallic materials by heating an adhesive filled with particles using an alternating magnetic field .

(Background technology)
In many industrial fields, in particular in the metalworking industry, for example in the automotive industry, in the manufacture of versatile vehicles and in the related supply industry, or in the manufacture of machinery and household appliances, and in the construction industry, Increasingly non-metallic substrates are joined by adhesives or sealants. Since bonding / sealing offers many technical benefits, this method of joining components is increasingly replacing conventional joining methods such as riveting, screwing or welding. This is particularly the case when joining metals to plastics and / or composites, or when joining different metals, for example joining materials of different composition, such as joining steel parts to aluminum or magnesium parts. That is true.

  In the industrial field, particularly in automobile manufacturing, one condition that current manufacturing processes are required to meet is that the various bonded parts are quickly subjected to subsequent processing. The basic disadvantage of reactive adhesive systems is that it takes a relatively long time to cure the adhesive and thus increase its strength. This fundamental disadvantage is less pronounced for hot melt adhesives, but non-reactive (non-post-crosslinkable) hot melt adhesives are limited in scope, especially when high strength adhesive bonds are involved. It can only be exposed to high temperatures. When reactive adhesives are used, heating generally accelerates the curing process to a very high degree, thereby increasing the strength very quickly. For this purpose, workpieces which have already been bonded with an adhesive are generally heated. This can be done in various ways, for example by direct exposure to a flame in a large oven, hot air blower, workpiece or area of the workpiece to be bonded, or to an IR heater. Thermosensitive workpieces cannot be treated in this way and therefore require a method of heating only the adhesive. Such selective heating of the adhesive is known in principle. For example, WO 99/09712 discloses a method for at least partially curing sealants and adhesives by exposing at least a portion of the sealants and adhesives to microwave energy, particularly in direct automotive glass mounting. doing.

The use of microwave energy to heat non-conductive materials is known per se. A comprehensive description of this method can be found in R.A. V. Decahau and R. A. It is described in "Microwave Processing and Engineering" by Peterson, VCH Verlagsgesellschaft, 1986.

  The use of microwaves to cure polyurethane systems as present in adhesive compositions is also known in principle (US Pat. No. 4,083,901). However, in these known methods using microwave energy, the heated substrate is most often exposed to the microwave field in a large enclosed chamber such as a large oven or belt dryer. Unfortunately, such methods are not applicable when forming bonds and seals on large and difficult items such as car parts or the entire car body, and only a very small area for the entire size of the part. Exposure to microwave energy.

  The amount of microwave energy supplied to the partial or complete curing process depends on various factors, such as the viscosity of the sealant and adhesive used and the thickness of the layer being cured, and the amount supplied is high The higher the viscosity of the sealant and the adhesive, the thinner the layer.

  In order to solve these problems, WO 88/09712 proposes to apply microwave energy in pulses using a specially designed emitter, providing a first group of pulses with reduced pulse amplitude. Is done. This pulsed application of microwave energy initially provides a relatively large but short energy supply, thereby heating a portion of the sealant and adhesive to a significant degree without signs of burning or degradation. Between the delivery of the first microwave pulse and the delivery of the next second group of pulses, thermal conduction causes temperature equalization in the sealant and adhesive, whereby the next pulse is initially heated relatively strongly. Does not cause overheating of the sealed sealant and adhesive parts. The heating action of the first pulse and the resulting temperature increase of the sealant and adhesive can expose the sealant and adhesive to microwave pulses of decreasing amplitude, thus providing a small amount of energy. In practice, however, this method has been shown to be difficult to control the amount of energy and is limited to cases where very short cycle times can be used for the joining process and hence curing.

  EP-A 545033 discloses a method for bonding electrical windings, in particular to the iron core of an ignition coil, using an adhesive that can be cured by heat. In this method, the winding and iron core are exposed to an alternating high frequency field, thereby heating them. In this way, the unit formed by the windings and the iron core is heated rapidly and homogeneously, thereby curing the adhesive. However, this method can only be applied to the structural aspects of certain electrical components.

  EP-A 237657 discloses a method for joining carpets. For this purpose, it is described that the adhesive layer contains a high frequency induction powder or that the adhesive tape contains a conductive metal foil. It has been proposed to introduce iron, cobalt, nickel, aluminum, carbon or graphite in powder form as a conductive or inductive material into a heat sensitive material. In order to facilitate heating by induction heating, these powder form particles preferably have a flat layer structure.

US-A 5833795 discloses a method for repairing composite materials by bonding repair patches to products made of composite materials. It has been proposed to use an epoxy adhesive containing magnetic particles, whereby the adhesive or epoxy resin is cured by electromagnetic excitation of the magnetic particles. In particular, it has proposed a microwave curing. For this purpose, magnetic particles such as iron silicide should be present in an amount of about 15-20% by volume, and the magnetic particles should have a Curie temperature in the temperature range required for curing.

  WO 98/05726 discloses a method for adhesively joining rubber parts. In this method, the surfaces of the rubber parts to be joined are placed beside a specific device. The device has a target element that absorbs electromagnetic waves and contacts the thermally activated adhesive. The electromagnetic wave heats the target element and activates the adhesive. The surfaces to be joined are brought together and the device is exposed to electromagnetic radiation, thereby generating enough heat to activate the adhesive and to fix the bond between the rubber part and the working surface. A very similar device is disclosed in WO 98/05728. According to this document, the device is particularly effective when used between components that are transparent to electromagnetic waves.

  WO 98/51476 describes a method of forming a system for transporting liquids, in particular a method of joining a rigid thermoplastic container to a flexible thermoplastic or thermosetting elastomer line formed using an electromagnetic joining method. Is disclosed. The flexible line is designed to ensure an accurate fit to the rigid container under compressive force. For this purpose, an electromagnetic curing adhesive is applied between the parts before applying the electromagnetic force. The adhesive material is described as a thermoplastic material containing at least 60% by weight of homogeneously dispersed particles that absorb electromagnetic energy.

Thus, from the prior art, two methods (first is to heat the device or substrate in close proximity to the adhesive layer by electromagnetic radiation, and second is to add particles that absorb electromagnetic radiation to the adhesive. , by dispersing) a very high percentage in the adhesive matrix, it may expose the adhesive electromagnetic radiation, but that is known, metal powder or other particles of such high percentages of absorbing electromagnetic radiation Especially in the case of high-strength adhesives, the strength of the adhesive thus cured is often very adversely affected.

(Disclosure of the Invention)
In contrast to this prior art background, the problem to be solved by the present invention is to effectively convert electromagnetic radiation into the heat required to heat the adhesive, adversely affecting the properties of the adhesive. It is to provide a way not to give.

The solution to this problem that the present invention provides is defined in the claims consists essentially of providing a method of heating an adhesive composition by an alternating magnetic field, the adhesive composition, nanoscale Contains superparamagnetic particles, so that upon exposure to radiation, in the case of thermoplastic adhesives, to the extent that the softening point of the thermoplastic binder is reached or exceeded, in the case of reactive adhesives The adhesive composition is heated to such an extent that the temperature at which the binder matrix is cross-linked by the reactive groups of the binder is reached.

The invention also relates to a method for bonding non-metallic materials and / or composite materials, which method comprises the following main steps:
· The nanoscale superparamagnetic particles adhesive composition containing, optionally after cleaning and / or surface treatment is applied to at least one substrate surface to be bonded;
Align the substrates so that the adhesive composition is between the substrates to be joined;
-The adhesive composition is cured by heating with an alternating magnetic field .

The present invention also relates to a similar method of joining metal materials and / or composite materials, the method comprising the following main steps:
· The nanoscale superparamagnetic particles adhesive composition containing, optionally after cleaning and / or surface treatment is applied to at least one substrate surface to be bonded;
Heating the adhesive composition with an alternating magnetic field ;
• Match the substrates so that the adhesive composition is between the substrates to be joined.

  The method of bonding materials may be performed in two stages. In the first stage, the adhesive matrix is only partially cured by thermal precuring or by UV radiation, and in the next stage it is fully cured by electromagnetic radiation. On the other hand, in the first step, the adhesive matrix is only partially cured by electromagnetic radiation, and in the next step, the two-step method can be performed by heat curing, moisture curing or UV curing. Good.

  The nanoscale particles in the present invention are particles having an average particle size (or average particle size) of 500 nm or less, more preferably 200 nm or less, most preferably 100 nm or less, and in one particularly preferred embodiment, 50 nm or less. The particle size in this rule means the primary particle size. Nanoscale particles used in particularly preferred embodiments of the present invention have an average particle size of 1-100 nm, more preferably 3-50 nm. In order to use the action of superparamagnetism particularly effectively, the particle size should be 50 nm or less. The particle size is preferably measured by the UPA (ultrafine particle analyzer) method, for example, laser light backscattering. In order to prevent or avoid aggregation or association of nanoscale particles, the particles are generally surface modified or surface coated. Corresponding methods for producing non-aggregated nanoscale particles, for example iron oxide particles, are disclosed in DE-A 19614136, columns 8-10. Such a nanoscale particle surface coating method to avoid agglomeration is disclosed in DE-A 19726282.

An alternating electric field or alternating magnetic field is suitable for introducing energy. When applying an alternating electric field, suitable filler materials are any piezoelectric compound, such as quartz, tourmaline, barium titanate, lithium sulfate, potassium tartrate, sodium tartrate, sodium potassium tartrate, ethylenediamine tartrate, perovskite ferroelectrics Material, in particular lead zirconium titanate. When using an alternating magnetic field, Shin'yu Ru superparamagnetic material, in particular, metallic aluminum, cobalt, iron, nickel or their alloys, and n- maghemite type (γ-Fe ₂ O ₃₎ and n- magnetite type (Fe ₃ O ₄ ) metal oxide, general formula: MeFe ₂ O ₄ ferrite [wherein Me is selected from the group consisting of manganese, copper, zinc, cobalt, nickel, magnesium, calcium and cadmium; Represents a valent metal] is basically preferred.

  When using an alternating magnetic field, nanoscale superparamagnetic particles, so-called single domain particles, are particularly suitable. Compared to paramagnetic particles known from the prior art, nanoscale fillers are characterized by having no hysteresis. As a result, there is no energy dissipation due to magnetic hysteresis loss; instead, heat generation is caused by particle vibration or rotation in the surrounding matrix, which is induced during the action of an alternating electromagnetic field, and ultimately mechanical friction loss. caused by. This results in a very effective heating rate of the particles and the matrix surrounding them.

The method of the present invention is particularly distinguished from conventional heating methods by the fact that the substrate material to be bonded is not subjected to thermal stress due to localized heat generation. The method of the present invention is extremely quick and effective because it does not involve the diffusion of heat to the substrate. Outstanding thermal losses occurring when even, is prevented by this method, thereby the method of the present invention is very economical.

  If the action of curing the adhesive must be carried out at a very low cost, it is possible to use ferromagnetic iron oxides and mixed oxides originally developed for electromagnetic recording media such as magnetic tapes or disks. It was shown to be effective. This is because they can be produced on a large scale at low cost and have corresponding utility. These metal oxides generally have a particle size of 200 nm to 1,000 nm and can be used in the present invention.

  Suitable matrices for the adhesive used in the present invention are in principle any polymer suitable for the adhesive. Examples of thermoplastic softening adhesives are ethylene / vinyl acetate copolymers, polybutenes, styrene / isoprene / styrene and styrene / butadiene / styrene copolymers, thermoplastic elastomers, amorphous polyolefins, linear thermoplastic polyurethanes, copolymers. Hot melt adhesives based on polyesters, polyamide resins, polyamide / EVA copolymers, polyaminoamides based on dimer fatty acids, polyesteramides or polyetheramides. Other suitable adhesives are in principle one or two component polyurethanes, one or two component polyepoxides, silicone polymers (one or two components), G. Habenicht, "Kleben: Grundlagen, Technologie, Anwendungen", 3rd edition, 1997, a known two-part adhesive based on a silane-modified polymer as described in section 2.3.4.4. Also suitable as an adhesive matrix are (meth) acrylate functional two-part adhesives based on peroxy curing agents, anaerobic curing mechanisms, aerobic curing mechanisms or UV curing mechanisms.

  Also suitable are binders based on one- or two-component reactive rubbers as disclosed, for example, in EP-A-356715, DE-A-19502381, DE-A-19518673 or DE-A-19730425. This method can also be used to cure adhesive / sealants or sealing compounds based on PVC homopolymers or copolymers, (meth) acrylate homo- or copolymers or styrene copolymers and plasticizers. For effective and rapid curing of adhesives at very low temperatures, especially use one-component polyurethane systems containing reactive counterparts or readily fusible polyols or amino-terminated prepolymers with dispersed solid surface deactivated polyisocyanates Yes. Such surface-inactivated polyisocyanate systems are, for example, EP-A-922720, US-A-5710215, EP-A-598873, EP-A-671423, EP-A-417540, EP-A-510476, EP -A-212511 or EP-A-131903.

  Among the binders, dispersions based on solid derivatives of toluene diisocyanate (TDI) such as TDI uretdione or TDI urea powder or isophorone diisocyanate (IP, -DI) trimer are particularly suitable. Such surface-inactivated polyisocyanates are powders, have a melting point of 95-145 ° C., a particle size of about 1 μm to about 30 μm, and a 50% average value of the particle size distribution is 8 μm to 2 μm. The advantage of these micronized solid diisocyanates is that the diisocyanates are substantially insoluble in hydrocarbons, many polyols and plasticizers at low temperatures, so that they can be dispersed in them and surface loss with suitable amines. It can be used.

  Preferred dispersants are liquid, glassy and amorphous or crystalline at room temperature, have 2 or 3 hydroxyl groups per molecule, and have a molecular weight of 400 to 20,000, preferably 1,000 to 6,000. It is a polyol which is a hydroxy compound. Examples are difunctional and / or trifunctional polypropylene glycols, but random and / or block copolymers of ethylene oxide and propylene oxide may also be used. Another group of preferred polyethers is, for example, polytetramethylene glycol (poly (oxytetramethylene) glycol, poly-THF) prepared by acid polymerization of tetrahydrofuran, the molecular weight of polytetramethylene glycol being 600-6,000. Preferably, it is 800-5,000.

  Other suitable polyols are liquid, glassy, amorphous or crystalline polyesters, which are dicarboxylic or tricarboxylic acids such as adipic acid, sebacic acid, glutaric acid, azelaic acid, suberic acid, undecane diester. Acids, dodecanedioic acid, 3,3-dimethylglutaric acid, terephthalic acid, isophthalic acid, hexahydrophthalic acid, dimer fatty acids or mixtures thereof and low molecular weight diols or triols such as ethylene glycol, propylene glycol, diethylene glycol, Ethylene glycol, dipropylene glycol, butane-1,4-diol, hexane-1,6-diol, decane-1,10-diol, dodecane-1,12-diol, dimer fatty alcohol, glycerol, trimethylolpropane or the like Mixing Obtained by condensation of. Another group of polyols suitable for the present invention are polyesters based on ε-caprolactone, also known as “polycaprolactone”. However, polyester polyols derived from oleochemicals can also be used. An oleochemical polyester polyol is, for example, a ring-opening of an epoxidized triglyceride of a fat mixture containing at least partially olefinically unsaturated fatty acids with one or more alcohols having 1 to 12 carbon atoms. And then by partial transesterification of the triglyceride derivative to form an alkyl ester polyol having 1 to 12 carbon atoms in the alkyl group. Other suitable polyols are polycarbonate polyols and dimer diols (Henkel KGaA) and castor oil and its derivatives. For example, hydroxy functional polybutadienes known under the trade name “Poly-bd” may also be used as polyols for the compositions of the present invention.

  Other suitable polyols are linear and can be prepared by radical copolymerization of acrylates or methacrylates with hydroxy functional acrylic and / or methacrylic acid compounds such as hydroxyethyl (meth) acrylate or hydroxypropyl (meth) acrylate. / Or a lightly branched acrylate copolymer polyol. Because of this production method, the hydroxyl groups of these polyols are generally statistically distributed, and the polyols are linear or lightly branched polyols having an average OH number. Bifunctional compounds are preferred for polyols, but higher functionality polyols may be used in at least small amounts. The solid polyol should have a melting point range of less than 70 ° C., preferably less than 50 ° C. and should have a low viscosity in the molten state, although polyols that are liquid at room temperature are particularly preferred.

  Many triamines or polyamines can be used in place of or in conjunction with the polyol, but amino-terminated polyalkylene glycols, particularly trifunctional amino-terminated polypropylene glycols, polyethylene glycols, or copolymers of propylene glycol and ethylene glycol are preferred. . These are also known under the name “Jeffamine” (trade name of Huntsman). Trifunctional amino-terminated polyoxytetramethylene glycol (also known as poly-THF) is also particularly suitable, amino-terminated polybutadiene, and aminobenzoates of polypropylene glycol, polyethylene glycol or poly-THF ("Versalink Oligomeric from Air Products"). Also known is the trade name “Diamines”. The amino-terminated polyalkylene glycol or polybutadiene has a molecular weight of 400 to 6,000.

In principle, the exchange Ban磁 boundaries of any relative frequency may be used as an energy source for heating of the adhesive containing nanoscale particles. For example, electromagnetic radiation in the range of the so-called ISM (industrial, chemical and medical applications) can be used (for details, in particular Kirk-Othmer, "Encyclopedia of Chemical Technology" 3rd edition, volume 15, "Microwave technology" See chapter).

  It has been shown above that when using the nanoscale particles of the present invention, electromagnetic radiation can be used for specific actions. This can result in the amount of heat needed to separate the adhesive binder matrix in the adhesive matrix using virtually any frequency, even in the low frequency range of about 50 kHz or 100 kHz to 100 MHz. This is clearly shown in the fact. The choice of frequency depends on the equipment used and should be taken care of so that no interference fields are radiated.

  The invention is illustrated below with a few basic tests. The choice of examples does not limit the scope of the invention in any way, and the examples are only models illustrating how to operate the adhesive composition of the invention.

(Example)
Tests examining the effect of nanoscale particles on thermal adhesives were performed using three thermoplastic hot melt adhesives available from Henkel KGaA. The hot melt adhesives are standard ethylene / vinyl acetate based adhesives (Technomelt Q 3118; EVA1) and medium heat resistant (Macromelt 6208; PA1) and high heat resistant (modified polyamide; PA2) This was an adhesive based on polyamide. The selection of characteristic adhesion or material properties of the unmodified adhesive is shown in Table 1.

To measure the heat resistance (HR) of the bond, two samples with 100 x 25 x 4 mm beech and PVC holes were bonded to a 20 x 25 mm area using an adhesive and then And stored at room temperature for about 24 hours. The bound sample was then suspended in a circulating air drying chamber (Heraeus UT 5050 EK) and a 1365 g weight was attached. The following temperature program was then applied:
1. Start at 25 ° C;
2. Heat to 25-50 ° C in 10 minutes;
3. Heat to 50-200 ° C in 5 hours;
4. Maintain at 200 ° C for 20 minutes;
5. Cool to 25 ° C in 20 minutes.

The time (seconds) required to break the bond was displayed by a microprogrammer (DEP 1131). Heat resistance (HR) was calculated based on the following formula:

  The tensile breaking strength (SS) was measured according to DIN 53283. Samples of 100 × 25 × 4 mm beech and PVC were bonded to a 20 × 25 mm area using an adhesive and subjected to tensile testing after approximately 24 hours (Zwick 144501 Universal Tester).

  The adhesive was modified with various amounts of nanoscale magnetite. The magnetite used was partially surface modified in order to better fit the polymer adhesive matrix. The particle sizes shown in Table 2 were determined by UPA (ultrafine particle analyzer) measurement. The crystal size of magnetite was 8 nm as determined by X-ray structural analysis.

  The magnetite of Table 2 was dispersed in the adhesive of Table 1 at various filling levels. The properties of some selected 20 wt% modified formulations are shown in Table 3.

  From Examples 4-8, it is clear that heat resistance and shear strength are generally not adversely affected even when the adhesive is highly filled with nanoscale magnetite. In the case of adhesives based on high heat resistant polyamides (PA2), when trying to obtain very high tensile shear strength, the amount of magnetite particles and the surface modifier are mutually, and on the substrate to be bonded, Should be adapted.

Example 9 :
Effect of “Signal Receptor” Particle Size on Induced Heatability of Modified Adhesive Basically, not only nanoscale “signal receptors” but also larger particle size signal receptors are responsible for induction heating of polymer matrices. Is preferred. However, as a result of other heating mechanisms not described in detail here, the amount of energy that can be introduced when using nanoscale particles is much higher than when using large particles. This can be shown, for example, by corresponding tests performed using a modified polyester system (Dynacoll 7360, Huels). The required alternating magnetic field was generated by a Huetttinger TIG5 / 300 generator. The applied voltage was 180V. The coil used had a diameter of 3.5 cm and 10 turns. It was part of an oscillator circuit that generates vibration. A frequency of about 250 KHz was obtained at the above voltage and dimensions. From Example 10 and the comparative example, when using nanoscale fillers as a “signal receptor” in an adhesive matrix according to the present invention, a much shorter time and at a much higher temperature than using “coarse” magnetite particles. It is clear that the modified polyester is heated. Table 4 shows the test results.

Example 10 :
Effect of “Signal Receptor” Fill Level on Induced Heatability of Modified Adhesive The heating behavior of the modified adhesive in an alternating magnetic field is highly dependent on the fill level of the signal receptor used. Corresponding tests were performed using magnetite modified EVA1 as an example. The required alternating magnetic field was generated using a Huetttinger TIG5 / 300 generator. The applied voltage was 180V. The coil used had a diameter of 3.5 cm and 10 turns.
The test results are shown in Table 5.

  From Examples 11-14, it is clear that the nanoscale magnetite filling level increases and the required heating time is significantly reduced under the same conditions otherwise.

Example 15 :
Effect of alternating magnetic field strength on induction heating properties of modified adhesives A critical factor in the dielectric heating of magnetite modified adhesives is the strength of the applied magnetic field. The strength of the magnetic field generated in the coil depends in particular on the applied voltage or flowing current. Tests measuring the effect of various voltages were performed using a Huetttinger TIG5 / 300 generator. The maximum voltage applied was 180V. The coil used had a diameter of 3.5 cm and 10 turns. The composition of Example 8 was used as an adhesive. The results are shown in Table 6.

  From the data in Table 6, the heating rate of the adhesive matrix increases significantly with increasing magnetic field strength (ie, increasing applied voltage), thereby melting the adhesive matrix and thus bringing the two substrates together. It is clear that a temperature sufficient for bonding is reached in a very short time.

Example 16 :
Effect of coil shape on induction heating properties of modified adhesive The magnetic field strength of an alternating magnetic field depends not only on the applied voltage but also on the length and number of turns of the coil used. At constant voltage, magnetic fields of various frequencies or strengths are obtained depending on the coil length and the number of turns. Corresponding tests were performed at a maximum constant voltage of 180V. PA2 modified with 20 wt% magnetite was used as the adhesive base. The coil used had a constant diameter of 3.5 cm and the number of turns was different. The results of these tests are shown in Table 7.

  The results shown in Table 7 show that the heating rate is significantly increased for the same adhesive composition when using shorter coil lengths or fewer turns and the resulting higher magnetic field strength.

  In order to determine how much the induction heating changes the properties of the adhesive, a test was conducted in which PA2 modified with 20 wt% magnetite was dielectrically heated several times. A Huettinger TIG5 / 300 generator was used for testing. The applied voltage was 180V. The coil used had a diameter of 3.5 cm and 10 turns. The results obtained show that the heating behavior of the modified adhesive was not substantially affected even after repeated heating with an alternating magnetic field.

  Thus, a thermoplastic adhesive can be used to make the heating and hence the bonding of the substrates reversible, so that the bonded parts can be repeatedly separated and rebonded if necessary. Can do.

  A one-component thermoset polyurethane adhesive (Terolan 1500, product of Henkel Teroson GmbH) was used to cure the one-component reactive adhesive. This adhesive is a polyurethane adhesive based on polyol, Jeffamine, catalyst and surface deactivated TDI dimer dispersed therein. In the examples below, the unmodified adhesive is referred to as “TcPU”. The adhesive was modified with various amounts of nanoscale n-magnetite. Correspondingly modified adhesive wood / wood adhesive bonds were exposed to an alternating magnetic field. It has been found that the cure rate depends to a large extent on the frequency and strength of the magnetic field used and the thickness of the adhesive layer. A Huettinger TIG 5/300 magnetic field generator was used. The applied voltage was 100% of the maximum possible with the generator used (180V). A 10-turn coil was used for the “weak” magnetic field, and a 4-turn coil was used for the “strong” magnetic field. Results selection is shown in Tables 8-10. The adhesive thickness was all 500 μm.

  From Examples 15-20, even when very small amounts of magnetite are used, the type of thermosetting reactive adhesives of interest cures in a very short time and is obtained by conventional oven curing of the same adhesive composition. It is clear that very high tensile shear strength can be provided, far exceeding the tensile shear strength that is achieved. From these tests, it is clear that the curing time of the adhesive can be remarkably reduced, particularly in the curing by electromagnetic waves according to the present invention. Accordingly, the thermal stress of the bonded substrates is also reduced.

Claims (13)

A method of heating an adhesive composition by an alternating magnetic field, heating an adhesive composition containing nanoscale superparamagnetic particles having an average particle diameter of 1 to 100 nm,
In the case of thermoplastic adhesives, heat to a temperature above the softening point of the thermoplastic binder,
In the case of reactive adhesives, heating to a temperature at which the binder matrix is crosslinked by the reactive groups of the binder,
A method characterized by that.
2. The method according to claim 1, wherein the nanoscale particles have an average particle diameter of 3 to 50 nm.
Nanoscale superparamagnetic particles are aluminum, cobalt, iron, nickel or alloys thereof, metal oxides of n-maghemite type (γ-Fe ₂ O ₃ ) and n-magnetite type (Fe ₃ O ₄ ) or general Formula: MeFe ₂ O ₄ ferrite, wherein Me represents a divalent metal selected from manganese, copper, zinc, cobalt, nickel, magnesium, calcium or cadmium The method according to claim 1 or 2.
The method according to any of claims 1 to 3, wherein the nanoscale particles are present in an amount of 1 to 30% by weight, based on the total composition.
The method according to any one of claims 1 to 4, wherein the alternating magnetic field to which the adhesive composition is exposed has a frequency of 50 kHz to 300 GHz.
6. The method according to claim 5, wherein the frequency is 50 kHz to 300 MHz.
6. The method according to claim 5, wherein the frequency is 300 MHz to 300 GHz.
The thermoplastic adhesive composition comprises ethylene / vinyl acetate copolymer, polybutene, styrene / isoprene / styrene or styrene / butadiene / styrene copolymer, thermoplastic elastomer, amorphous polyolefin, linear thermoplastic polyurethane, copolyester, polyamide resin, Polyamide / EVA copolymers, polyaminoamides based on dimer fatty acids, polyesteramides, polyetheramides, or plastisols based on PVC homopolymers and / or copolymers, (meth) acrylate homo- and / or copolymers or styrene copolymers and plasticizers The method of claim 1, wherein:
The reactive adhesive composition is based on a one or two component polyurethane, a one or two component polyepoxide, a silicone polymer, a silane modified polymer, a one or two component reactive rubber or one component polyurethane and a surface deactivated solid polyisocyanate; The method according to claim 1, characterized in that
A method for bonding non-metallic materials and / or composite materials comprising:
Applying an adhesive composition containing nanoscale superparamagnetic particles having an average particle size of 1 to 100 nm to at least one of the substrate surfaces to be joined;
Align the substrates so that the adhesive composition is between the substrates to be joined;
A method comprising curing the adhesive composition by heating with an alternating magnetic field.
A method for joining metal materials and / or composite materials comprising:
Applying an adhesive composition containing nanoscale superparamagnetic particles having an average particle size of 1 to 100 nm to at least one of the substrate surfaces to be joined;
Heating the adhesive composition with an alternating magnetic field;
• A method comprising the steps of aligning the substrates such that the adhesive composition is between the substrates to be joined.
Curing is carried out in two stages, characterized in that in the first stage the adhesive matrix is only partially cured by thermal precuring or by UV irradiation and in the next stage it is sufficiently cured by an alternating magnetic field. The method according to claim 10 or 11.
  Curing is performed in two stages. In the first stage, the adhesive matrix is only partially cured by an alternating magnetic field, and in the next stage, it is sufficiently cured by heat curing, moisture curing or ultraviolet irradiation. The method according to claim 10 or 11.